It is known to provide a foundation jacking tool assembly for use in stabilizing the foundation of a building, wherein a screw anchor or pier is driven into the ground adjacent the foundation, a support is positioned at the bottom of a foundation, a lifting force is applied to the support and foundation using the screw anchor or pier as a base for the lifting force applied to the support and hence the foundation so that the foundation loads are transferred to the screw anchor or pier. In particular, in the prior art applicant is aware of U.S. Pat. No. 5,120,163, issued Jun. 9, 1992 to Holdeman et al. for a Foundation Underpinning Bracket and Jacking Tool Assembly, U.S. Pat. No. 5,171,107, issued Dec. 15, 1992 to Hamilton et al. for a Method of Underpinning Existing Structures, U.S. Pat. No. 5,213,448, issued May 25, 1993, to Seider et al. for an Underpinning Bracket for Uplift and Settlement Loading, and U.S. Pat. No. 6,539,685, issued Apr. 12, 2003, to Bell et al. for an Apparatus and Method for Lifting Sunken Foundations.
As described by Bell et al. in U.S. Pat. No. 6,539,685, the slow settling of the foundations of buildings, concrete slabs, and other heavy structures is a phenomenon occurring occasionally in various areas, particularly where the underlying soil is not stable. As a result, various equipment and techniques have been developed for lifting sunken or settled foundations, slabs, etc. These techniques generally involve the digging of a hole or trench along the structure to be lifted, and driving one or more pipes or piers into the ground adjacent to the structure until the pipes reach stable material or the underlying bedrock. A lifting apparatus is then installed on the support pier and extended beneath a portion of the structure to be raised. Typically a hydraulic lift is used to lift the lifting apparatus and structure resting thereon. This process is conducted simultaneously every several feet as needed along the length of the structure being raised, in order to distribute the lifting forces generally equally along the structure.
Another problem incurred using many of the devices of the prior art, is that many such devices do not provide any form of mechanical locking to secure the lifting element (plate, arm, etc.) to its corresponding anchor pier or pipe. The lifting component is raised by one or more hydraulic jacks, but some means must be provided to secure the lifting component to the pier, before the hydraulic devices can be removed. Bell consequently provides an apparatus for lifting and stabilizing sunken or settled foundations, slabs, footings, etc. which includes a lifting plate having a pipe section solidly secured thereto, for passing concentrically over the anchor pier. A single clamp is adjustably positionable along the length of the pipe so that the clamp may be secured to a solid area of the foundation structure. The plate is secured to the pier using mechanical fasteners.